A direct printing technique (e.g., PictBridge) of directly connecting a digital camera and a printer by a physical interface, and directly outputting an image captured by the digital camera from the printer without intervening a PC is known. At this moment, a USB (Universal Serial Bus) is the mainstream of the physical interface. Such direct printing technique, however, does not depend on the type of physical interface, and can also use a wireless interface in principle. As the direct printing technique, a technique which allows a digital camera to capture an object while a protocol for direct printing is executed is known (Japanese Patent Laid-Open No. 2006-94376).
Depending on a protocol for a direct printing technique, a digital camera may not be able to release a connection until print processing by a printer is completed even if image data transfer is complete. If, for example, a connection between the digital camera and the printer is disconnected during the print processing, a print error occurs, and a paper sheet midway through the print processing is discharged.
In particular, if a protocol for direct printing is executed using a wireless interface, a problem may arise. This is because if image data transfer from the digital camera to the printer is completed and then the user of the digital camera moves it away from the printer to disconnect a wireless connection, it is impossible to guarantee the operation of the printer.